Add a tkinter.systray module wrapping the tk systray and tk sysnotify commands (Tk 8.7/9.0 and newer), which display a system tray (or taskbar) icon and send desktop notifications.

• SysTrayIcon wraps tk systray. Only one icon exists per Tcl interpreter, so SysTrayIcon is a handle to it: with exists=False (the default) a new icon is created (and a second one raises TclError), and with exists=True the instance refers to the already-existing icon. It supports the image, text, button1 and button3 options, configure()/config(), cget(), exists() and destroy().
• notify() and SysTrayIcon.notify() wrap tk sysnotify. On Windows a notification requires an existing tray icon, so the module function is for the other platforms and the method for Windows.

The tests require a GUI and create a real tray icon, so they are skipped where one cannot be created.

• Issue: Add a tkinter.systray module for system tray icons and desktop notifications #153259